UC Merced

Electric Vehicles (EVs) are emerging as the future of transportation as the marketmoves towards electrification. However, materials and lubricants for EVs have not been optimized over decades of tribological research like it has been done for internal combustion engine vehicles (ICEVs). Although EVs are more efficient than ICEVs, energy losses and tribological challenges in electric motors (EMs) are still considerable, so characterization of EM-specific friction and wear behavior is important. Particularly, greased bearings in EMs are subject to a wide range of operational requirements and corresponding micro-environments. Consequently, greases must function effectively in these conditions. Here, the tribological performance of four market-available EM greases was characterized by measuring friction and wear of silicon nitride sliding on hardened 52100 steel. The EM greases evaluated had similar viscosity grade, but different combinations of polyurea or lithium thickener with mineral or synthetic base oil. Measurements were performed across a range of temperatures and surface roughness conditions to capture behavior across multiple lubrication regimes. Results enabled direct comparison of market-available products across different application-relevant metrics and the analysis methods developed can be used as a baseline for future studies of EM grease performance.